In the manufacture of diamond tools by hot sintering, with or without pressure applied, of an intimate mixture of diamonds and of a binder material, use is made for the binder phase, that is the material forming the matrix of the tool after the sintering operation, either of fine cobalt powders (from less than 1 to about 6 .mu.m in diameter as measured with the Fisher Sub Sieve Sizer, called hereafter Fisher SSS) or of mixtures of fine powders, such as mixtures of fine cobalt, nickel and iron powders, or of coarse pre-alloyed powders, such as steel powders obtained by atomization of a melt.
The use of fine cobalt powder gives very good results from a technical standpoint; its major drawback stems from the high price fluctuations of the cobalt powder.
Using mixtures of fine powders, matrices are obtained whose strength, hardness and wear resistance are relatively low. The use of coarse pre-alloyed powders (from 10 to 50 .mu.m) requires high sintering temperatures, in the order of 1000 to 1300.degree. C., at which temperatures severe degradation of the diamonds takes place, resulting in weakened diamond crystals and poor retention of the diamonds in the matrix.
In SU-A-1689053 an iron-based metallic binder for diamond tools with improved tool performance, and containing Ni, Cu and C and Sn, is described. No specifications are given concerning the preparation of the binder and the characteristics of the powders involved.
The object of the present invention is to provide fine pre-alloyed powders, containing copper and iron as two of the alloying elements, and with less or no dependence on cobalt, whose use as a binder in the manufacture of diamond tools by hot sintering avoids the aforementioned drawbacks.